The typical reproductive system of female hexapods features paired ovaries which release eggs into lateral oviducts (Chapman 1998, Stys & Bilinski 1990). The egg then travels through the median oviduct to the genital chamber (vagina). Fertilization usually occurs immediately before oviposition by sperm that are retrieved from one or more sperm storage organs (spermathecae). In most hexapods, there is a delay between sperm transfer from the male to the female and sperm usage by the female; so sperm are often stored in spermathecae for considerable periods of time (up to many years in some ants, e. g., Tschinkel 1987).
Sperm are usually received through the female genital opening (gonopore), which also serves as the exit for fertilized eggs. In most insects, eggs are laid through an ovipositor, a tube-like structure of varying length created by the fusion and modification of the abdominal body wall (Chapman 1998, Lawrence et al. 1991, Weidner 1982). Upon leaving the body, hexapod eggs are often accompanied by the excretions of female accessory glands. These substances may be used to attach the eggs to the substrate, or they may protect the eggs from predators or the elements (Chapman 1998).
In the male reproductive system, paired testes release sperm into the vasa deferentia which may feature a seminal vesicle where sperm are stored before leaving the body through the ejaculatory duct (Chapman 1998). The male accessory glands secrete seminal fluid, which supports sperm survival and fertilization success. Accessory gland secretions also form the spermatophore, a specialized structure that encapsulates sperm and seminal fluid and protects them during transfer to the female (Chapman 1998).
In apterygote hexapods (Collembola, Diplura, Archaeognatha, Zygentoma, nothing is know about the mating behavior of Protura) sperm transfer is indirect; i. e., males deposit (usually stalked) spermatophores in the environment, and females actively pick up sperm packets and absorb them into their reproductive tract (Proctor 1998, Schaller 1971). In pterygote insects, spermatophores or unencapsulated sperm are usually transferred directly from male to female through copulation, and males have highly specialized intromittent organs for this purpose (Chapman 1998, Eberhard 1985).
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